## 代碼實現
利用二分查找,返回一個數在數組的索引位置,必須是有序數組
```
let arr?=?[1,?2,?3,?4,?6,?7,?8];
function test(arr,?val)?{
let low?=?0;
let high?=?arr.length?-?1;
while?(low?<=?high)?{
let mid?=?parseInt(?(low?+?high)?/?2?);
if(val?==?arr[mid]){
return mid;
}?else if(val?>?arr\[mid\]){
low?=?mid?+?1;
}?else if?(val?<?arr\[mid\]){
high?=?mid?-?1;
}
?}
return?-1;
}
test(arr,?5);
```
